Common motor vehicle fuel injection systems include an in-tank fuel pump assembly with an electric motor driven high pressure pump stage, a high pressure fuel rail, and a low pressure return pipe for returning surplus fuel from the fuel rail to the tank. Typically, the high pressure pump stage is a roller vane positive displacement pump. Recently, attention has been focused on motor vehicle fuel injection systems, referred to as "Demand Systems", in which the discharge of the high pressure pump stage is controlled to match engine demand by modulating the speed of the electric motor. Demand Systems are attractive because they do not require apparatus for returning surplus fuel to the fuel tank and because they do not require apparatus in the tank for segregating surplus fuel, which is usually hot, from bulk fuel, which is usually relatively cool. A roller vane high pressure pump stage according to this invention is particularly suited for application in electric fuel pump assemblies in Demand Systems.